When a patient is a candidate for an implantable therapy, an implantable lead or catheter may be implanted and a lead extension or a catheter extension may also be necessary depending upon the location of the therapy site. For example, with stimulation therapy such as sacral nerve stimulation therapy, spinal cord stimulation therapy and the like that may be used to treat conditions such as incontinence or chronic pain, it is often desirable to conduct a trial period of stimulation. This trial period allows an external stimulator to be used so that the patient is not required to undergo a full stimulation device implantation procedure but calls for a lead extension to extend between the lead and the external stimulator. If the trial is successful, then an implantable stimulator is fully implanted into the patient.
When implanting the trial system, an implantable medical lead is implanted with a distal end being routed to the stimulation site. The proximal end of the lead is routed to a pocket away from the entry site. An implantable lead extension is typically then routed subcutaneously from the location of the proximal end of the implanted medical lead to an exit site nearby the location where the external stimulator will be mounted to the patient. An external lead extension is then used to interconnect the exposed proximal end of the implantable lead extension to the external stimulator. Alternatively, the implantable lead extension may be provided with enough length to reach the external stimulator and is further provided with a connector for direct connection to the external stimulator.
During the implantation of the lead extension or a catheter extension, the lead extension or catheter extension is pulled through a subcutaneous tunnel. One manner of doing this is to utilize a carrier on the end of the tunneling tool, where a connector body of the lead extension is placed within a cavity of the carrier. However, this requires the carrier to be removed from the tunneling tool during the tunnel creation to avoid the cavity of the carrier snagging on and collecting tissue and then attached prior to pulling the lead extension through the tunnel. This adds unwanted steps to the surgical procedure. Another approach is to place a cover around the carrier while the carrier is on the tunneling tool, but in some cases the approach creates a larger diameter around the carrier during tunneling which may make the tunneling process more difficult.
Rather than a carrier, a pin located on the tunneling tool may be inserted into a lead bore of the connector but this requires a set screw or other fastener to be manually tightened onto the pin in order to create an engagement of the pin to the connector which further complicates the implantation procedure. Furthermore, the pin does not provide adequate coupling in order to successfully pull a catheter extension through a subcutaneous tunnel.